Rope

[Jesse Frank]

Hi all,

I have a quick question.

I'm getting together all the stuff I need to raise my shop, and one issue I've run into is finding the right rope. There doesn't seem to be a consistent way to rate them. For instance, I've seen polypropylene rope that states something ridiculous like 3000 pounds, but when you actually get it it has a working load of only 350 to 400 lbs.  I need to use it in conjunction with my block and tackle and winch to raise the bents. Any suggestions?

Thanks!
Jesse

[beenthere]

One place I read where the tensile strength is given, and then the 5% safety factor given, such as:

""...has a tensile strength is rated at 2,250 lbs. At a 5% safety factor, that's a safe working load of 112 lbs."

Additional finding:

""Interpretation of Rope Strength
     One area of misunderstanding that needs to be brought to the surface is the proper interpretation of rope strength, appropriate usage and care. Let's start by defining two important terms: "tensile strength" and "working load". Tensile strength is the average strength of new rope under laboratory conditions. This is determined by wrapping the rope around two large diameter capstans and slowly tensioning the line until it breaks. The manufacturer's recommended working load is determined by taking the tensile strength and dividing it by a factor that more accurately reflects the maximum load that should be applied to a given rope to assure a comfortable safety margin and longevity of the line. Of course that factor varies with the type of fiber and the weaving construction. There are however always exceptions, most notably the fact that rope is susceptible to degradation and damage in numerous ways that are not controllable by the manufacturer.
     It may surprise you to find out that the working load for most kinds of rope is between 15% and 25% of the tensile strength. Now consider the fact that any time you tie a knot in a rope you effectively cut the tensile strength in half. The knot when tensioned cuts the line. While certain kinds of knots damage the line less than others, the 50% loss of tensile strength is a good general rule to live by. Research has shown that the figure 8 knot reduces the tensile strength by approximately 35% instead of 50% for other common knots tested."


Hope it helps...I learned some things too...

[Dave Shepard]

For any overhead work, a good rope is ideal. The stuff you get at the hardware store is probably not the best. Arborist ropes are rated in two ways. Climbing lines are 10% i.e. my line is rated for 8100 pounds, and has a safe load of 810. Rigging line is 20%. Rigging line would be good for overhead lifting of beams and bents. It is of a different makeup than climbing line, it doesn't generally have as much give, which is important. You don't want a squishy rope, one that will stretch greatly allowing for poor control. Check out the Baileys-online link to the left. They will have arborists rigging ropes. You will get a better understanding of how they are rated. A good rope might be a $1 a foot (or more?) but well worth it, something you will own for a long time. Remeber, ropes don't like heat or friction. ;)


Dave

Beenthere, you added a little more while I was posting. There are different types of "knots" These are knots, hitches, and bends. Each has a strength reduction rating. I have a list of the common ones, but I don't know where it is. I believe the bends have the least reduction but I could be wrong.

[Jesse Frank]

Thanks!  I found some dacron rope on ebay just now that has a 4200 pound WORKING load and a tensile strengeth of 24000 pounds

Do you think this will work?

http://cgi.ebay.com/wire-pulling-rope-anchor-rope-1-2-x-100-doublebraid_W0QQitemZ160201803216QQihZ006QQcategoryZ66986QQtcZphotoQQcmdZViewItem

[Jesse Frank]

That list of knots would sure come in handy if you wouldn't mind posting it!

[logwalker]

There are a couple things that worry me about that rope. They are calling it anchor line and there is no brand name. I would try to find a brand such as Sampson , New England Rope or some other well known and respected name to buy.

As far as anchor line goes it is made to stretch at least 15% or more to take shock loads at anchor. Makes it a bit hard to work with sometimes. I doubt that the line in the ebay ad is really anchor line seeing that it is double-braid.

Buy good line and take good care of it and it will return the favor

[moonhill]

Jesse, I see you found some ansewers over here.  I would still like to know a brand name and a general all around  size.  Something one could use for guy lines as well as lifting, maybe a compromise 5/8" or 3/4" three strand, or something braided.  Cost should be a concideration.  There is something about being able to put your hands on a product and feel it before you lay out $600 for a spool, than find you don't like how the knot ties.  This has been my hold up to buying a spool.  I have tried lots of rope and still am not satisfied.  Maybe I should try Baileys and see it they send out samples.  By the way my favorite knot is the bowline, how does that standup in the weekness test, probably depends on how its used?   Tim B.

[beenthere]

Tim (moonhill)
While prowling around for knot strength reduction, I found this link
http://www.caves.org/section/vertical/nh/50/knotrope.html

Actual strength tests of various knots/ropes/replication was reported. The bowlin knot (my favorite) was on the list. I didn't check out some of the others that were ranked higher, but seems there was a figure 8 that was a bit higher strength. A comment was made about the strongest knot also was near impossible to untie. One thing I like about the bowline (bowlin) knot.  Also, 'joining' knots required a knot in the ends to keep the knot from untying (at least that was my interpretation)..

The Navy guys can prolly lend some knot tying knowledge to this ...

[Radar67]

Remeber, ropes don't like heat or friction. ;)

They don't like sand, sun, or water either. Working with a wet rope decreases strength. Sand gets under the cover and slowly cuts the inner core of the rope. Sun will deteriorate the rope over time, never store a rope where the sun can shine on it. And most important, inspect the rope before every use. If it is visibly frayed, crushed, or worn, don't use it.

A static climbing rope has much less stretch than a dynamic rope and is a little stiffer. You can still tie easily with it. The figure 8 knot metioned is a great all around knot and is easy to tie once you get used to it.

[sawguy21]

Here is a great site for knots
http://www.animatedknots.com/

[Tom]

The material that is used to make the rope is the most important after strength
wire rope doesn't stretch but is hard on your hands  :D

Dacron doesn't stretch but is one of the strongest and will give touighness with smaller sizes. (not stretching means that there is better control of a load, but no warning to failure.

Poly has no stretch but floats.  It is bothered by SUV from the sun much more than nylon

Nylon is heavy, stretches and is quite strong.  It is used where you need force stored in the line.   That's one reason it is used as a tow rope or snatch rope.

Natural fibres vary in strength but usually good to grip with your hand and hold knots  best.  You really have to pay attention to them , they will rot.

http://www.42brghtn.mistral.co.uk/knots/42ktmenu.html
http://www.netknots.com/

[beenthere]

Thanks
Great sites on knots...I've been practicing some of them.

One I use often has been called the Truckers Knot. Put a loop in the line to use to cinch up a load.
Also a Lorry knot
http://www.douglasbsa.com/knots/truckers.html

[zopi]

Actual strength tests of various knots/ropes/replication was reported. The bowlin knot (my favorite) was on the list. I didn't check out some of the others that were ranked higher, but seems there was a figure 8 that was a bit higher strength. A comment was made about the strongest knot also was near impossible to untie. One thing I like about the bowline (bowlin) knot.  Also, 'joining' knots required a knot in the ends to keep the knot from untying (at least that was my interpretation)..

The Navy guys can prolly lend some knot tying knowledge to this ...

you rang?  ;D

For reasonable rigging requirements, I much prefer chain falls, if i can possibly get them,
If i have to use rope, I'll generally use three strand nylon..rated well above the loads
I plan on lifting, or similarly kernmantle climbing rope..but that stuff doesn't react well to
dirt/oils whatever..

rule of thumb...an overhand knot reduces the strength of the rope (tensile) by 50% other knots
or bends by a greater or lesser amount..so i try knot to use them..eye splices with or without thimbles, and clevises or 'biners depending on the load, and good web strap load slings..i pretty much never tie a working line to anything being lifted..or If I do I'll use a doubled figure 8...

a good reference is Ashley's book of knots..a lot of the rigging depicted there is tried and true
from sailing ships...

do please keep in mind that these are things i do based on my experience..not necessarily what
modern industry recommends...

oh..synthetic lines will kill you..there is training that every young sailor gets that graphically
depicts what happens with synthetic line snapback..I've seen mooring lines snap and
wipe out half the bitts and liferails on the fo'csle of a destroyer..

if you google "synthetic line snapback," I'm sure the video is on the web somewhere...

here's a link to a PPT >snooze< that covers some deck safety stuff..most of it probably
doesn't apply to whatever you guys do..and if not there are some cool pictures in it...

http://www2.ku.edu/~kunrotc/academics/101/DECK.ppt

[Tom]

Cool slide show

[Thehardway]

A good source for rope and blocks/rigging materials.  http://www.mikekellerltd.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=MKL1&Category_Code=NETT1

They will send you a catalog.

They sell rope wholesale if you are getting any kind of qty. People in the commercial fishing/boating industry probably know more about rope and working strengths than just about anyone else.  They also sell specialty rope for climbing and arborists etc. 

They have dacron rope and can give you the true specs on it.

If I do rig up a gin pole on my job this is probably where I will get my rope and blocks/pulleys.

[LeeB]

Did you maybe have the poly and the nylon backwards as pertains to sun damage Tom?

[Tom]

Yes, Lee. I misspoke.  I was speaking of polypropylene when I said Poly and it is highly affected by UV, a lot more than nylon.   I'll edit my post.

[moonhill]

Sawguy21, post #9, that site even has the neck tie with 3 versions,  that is for special occasions.  But I couldn't find how it holds up under stress.  Other wise a great site.  Tim B.

[Dana]

Woodhick has rope listed for sale on that board.